I'm gonna guess based on switch positions that original equipment was the "Gravity I" ballast and the rear bags were added later. I have replaced a couple sprinkler valves on a 2008 so I would not be surprised if yours are junk by now. You are right they need to be in the "closed" position. You might want to upgrade the whole system but if you just want to replace sprinkler valves, use the Irritrol ones. They are better stuff and have better flow. I got mine at a local sprinkler sales place but you can get them online too:

http://www.sprinklerwarehouse.com/Ir...lves-s/433.htm